RF (Radio Frequency) systems and high speed digital systems require high Q (Quality Factor) passive components, such as capacitors, inductors, and transformers. These components are used in part to ensure that the analog RF and power supply circuits of the chip provide the accuracy necessary for any of a variety of RF functions, such as filtering, amplification, demodulation, upconversion, etc. and for digital processing. For cellular telephones, computers, and a wide variety of other radio equipped devices, RF chips are used to process analog and baseband radio signals. These chips are packaged for protection and to make them easier to mount to a circuit board.
Because it is difficult or expensive to produce sufficiently high Q passive components in a silicon semiconductor chip, passive components are often made separately from the chip and connected to the chip through an external connection. The components are then placed inside the package on the package substrate or in some cases on the outside of the package.